1. Field of the Invention
The present invention relates to a liquid chromatograph.
2. Description of the Related Art
A Liquid chromatograph involves little qualitative information. Accordingly, eluted components have been fractionated and subjected to qualitative analysis using other analytical instruments after optionally concentrating the eluate for correct identification and recognition of sample components.
While an analytical method in which the liquid chromatograph is used with on-line connection to another analytical instrument, such as a mass spectrometer, has been employed, most of the eluate has been split and discharged because the volume to be introduced into the other analytical instruments is limited. While a micro-liquid chromatograph using a column with a column inner diameter of 1 mm or less is effective for reducing the consumed solvent volume, a precise injection of the solvent with an injection volume of as small as 1 microliter or less is required.
However, it costs much labor for the liquid chromatograph to fractionate eluted components and inject them into a qualitative instrument, besides involving a risk of denaturation and loss of the sample components during the concentration process as well as mingling of foreign substances.
In addition, splitting of the eluate for on-line connection of the liquid chromatograph to another instrument such as the mass spectrometer may adversely affect quantitative analysis and sensitivity, although this method is effective for the analysis by the mass spectrometer.
Since the injected solution should form a band as narrow as possible for attaining high resolution among the chromatographic peaks, a large volume of the sample solution cannot be injected even when the sample concentration is low.
It is an object of the present invention to provide a liquid chromatograph that is able to assay a sample after concentrating the sample solution containing low concentration of components.
The present invention provides a liquid chromatograph comprising a first solvent flow line for diluting a sample solution with a first dilution solvent pump via an injector and for sending the diluted sample solution, and an analytical line for flowing an elution solvent into a flow passageway connecting through an analytical column to a detector using a solvent pump. The first solvent flow line and the analytical line are connected to a switching valve, respectively. The switching valve comprises a concentration column, the concentration column being freely connected to the first solvent flow line and analytical line by switching the switching valve. A second solvent flow line for sending a dilution solvent with a second dilution solvent pump is connected by providing a joint between the injector and switching valve. The sample solution as used herein refers to a solution containing a sample.
In order to omit off-line fractionation and concentration processes that involve much labor, a micro-liquid chromatograph that enables the volume of split solvent to be reduced is utilized with on-line connection to another analytical instrument such as a mass spectrometer, wherein injection of a large volume of low concentration sample solution is enabled by providing a sample concentration step.
In addition, the mixing ratio between the solvents from the first dilution solvent pump and the second dilution solvent pump at the joint may be adjusted by controlling the flow rates of the first and second dilution solvent pumps, enabling the degree of dilution of the sample solution to be freely determined.
It is known in the liquid chromatograph that the solvent used for the sample solution may affect separation of the sample components. Therefore, the volume and composition of the injected solvent introduced into the analytical line should be modified to the preferable composition of the solvent upon analysis using the liquid chromatograph. Appropriate analytical conditions may be employed in the liquid chromatograph according to the present invention, because the solvent for the sample to be trapped on the concentration column, i.e., the solvent to be introduced into the analytical line, can be diluted or substituted with the dilution solution.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.